The
large-scale study has more than doubled the number of known Alzheimer's susceptibility genes to 21. The research, reported in the
journal Nature Genetics, also identified another 13 possible risk genes for further
analysis.

Dr Gerard Schellenberg, one
of the leading researchers from the International Genomics of Alzheimer's Project, said: 'Here we greatly
increased the list of possible drug target candidates for Alzheimer's disease,
finding as many new significant genes in this one study as have been found in the
last 15 years combined. This international effort has given us new clues into
the steps leading to and accelerating Alzheimer's disease'.

By pooling together previously studied and newly
collected DNA data from a total of 25,500 Alzheimer's disease patients and
49,038 controls, researchers
found changes
in DNA that were more common in patients with the disease.

The genes linked to Alzheimer's risk are involved in a
number of different cellular pathways. The
most significant association was found in a region that plays a role in the
immune system and inflammatory response, and is also associated with a risk of multiple sclerosis and Parkinson's disease.

This work confirms the complexity
of Alzheimer's disease, but it may allow researchers to better understand the
causes of the disease, which could then be used to develop better treatments.

Dr Margaret Pericak-Vance, a lead researcher based at the University of
Miami, said: 'The discovery of novel pathways is very encouraging
considering the limited success of Alzheimer's disease drugs tested so far. Our
findings bring us closer toward identifying new drug targets for Alzheimer's
and other neurodegenerative diseases'.

Despite the results
being promising, researchers were also keen to point out that more work needs
to be done.

Dr
Schellenberg said: 'Alzheimer's is a complex disorder, and more
study is needed to determine the relative role each of these genetic factors
may play'.

Dr Julie Williams from Cardiff University
led the work in the UK. Speaking to the Daily Mail, she agreed that the
findings need to
be followed up with 'great urgency' to determine exactly how the genes cause
dementia. She added: 'I do think that in ten years' time we might
be looking at a genetic therapy. That might be feasible but not quite yet'.